Synchronous motor



BEST AWLABLE co V. A. .FYNN

SYNCHRONOUS MOTOR Filed Feb. 18 1924 Patented Sept. 14, 192 5.

i seer AVAlLABLE co'P VALEREALFRED FYNN, on sat LoUIs,' mIssoUm..

SYNCHRONOUS MOTOR.

7 Application filed February 18, 192 4. Scrial 1 l'o. 8B3,561.

My invention relates to the starting and operating'of dynamo electric machines in which arevolving field of more or less unifornrmagnitude is produced at least during the starting eriod. It relates more particularly to p0 yphase synchronous induction motors.

The objects and features of this invention will appear from the detail description taken in connection with the accompanying drawings and will be pointed out in the claims.

In the accompanying diagrammatic draw.- ings F ig. 1 is a two-pole three-phase embodiment of the invention and Figs. 2 to 9 inelusive are explanatory two-pole diagrams.

Referring to Fig. 1, the rotor carries a three-phase winding 3 adapted to be connected to the three-phase supply 7 8, 9 through the slip-rings 1, 5, 6 and a commuted wind- 'ing 2 ,with which co-operate two sets. of brushes 1O, 11 and 12, 13;these brush sets are displaced by more or less than 90 electrical degrees according to which of thebrushes this statement refers. Thus if refcrence is had to brushes 10 and-12, the displacement is less and if reference is had to brushes '1 and 13, it is more than 90 degrees.

The result is the same. \Ve will say that the brushes in Fig. 1 are displaced by less than 90 degrees.

' as 1O, 11 through the adjustable resistance 15.

The exciting winding canv be shunted and short circiuted by means otthe ad ustable resistance 26. The starting winding 18,:also

I located on the stator, is displaced 90 elec.-. 4b titical degrees from the exciting and com ;.the winding 1 1, the latter willproduce in \pounding winding and can be shunted and short-circuitcd by means of the athust'abie resistance 1S). This winding, together with' 14 or 16 or'withboth of these, forms 4; polypha'se arrangement of windings onthe secondary.

To start this mot -r," res istance 26 maybe Omitted in which case resistances 19 andflr' and, if desired, 15 are set to give as nearly balanced two-phase induction motor'torque as possible when the primary is connected to a source ot'phase-displaced voltages. As the'motor gathers speed the resistances can be diminished in one or more steps,"19-being finally short-circuited and 15 and .17 setjto their synchronizing and then to their opera-.

The stator carries an exciting winding 16 connected to the brushes 12, 13

-windings 14 and 16 by conduction from-the commuted winding 2. After synchronism'- is reached, both auxiliary or brush voltages become unidirectional and they, supply the unidirectional magnetization to the secondary.

While not strictly correct, it'is convenient to refer tojthe'brushes 10, 11 as the compounding and the brushes 12, 13 as the exciting brushes. The power factor variation witlrload can be influenced and varied within wide limits by changing the relation of the ampereturns in- 16 and 14 with refer ence to the ratio of the exciting to the compounding voltages or by displacing'one or both-brush sets-'or bytwo or more of the methods according to circumstances and withdue regard to the .best utilization of the copper in the commuted winding and tl 1e va'lue and conformation of the synchroniz ng torque. 1

A more uniform.induction motor torque can be had at starting and the commutator can be relieved of much of the starting cur'-' rent if the winding 16 is shunted by the resistance 26 during the earlystages of the starting operation. In that case, it is best to give :15 and 17 a high {value at the moment of starting. -As the speed increases,

the values of 15, 17 and 19 are reducedand' that of 26 increased and this resistance finally disconnected. These changes can be. made in'one or more steps according to the size of the motor.

When the brushes 10,111 are coaxial with conjunction with the primary re'volving'flux a ;.-strictly unidirectional pulsating torque and the same holds true of the brushes 12, "13-and the winding'lfi. When the brush axis displaced from the winding to which the brushes in that axis are connected, then the synchronizing torque exhibits a unidirectional"pulsatingand an alternating com ponent of double slip frequency with equal positive and negative maxima. The latter increases as the displacement increases and when the displacement reaches 90, electrical degrees the amplitude of the alternating torque component is a maxim um and the unidirectional torqueis nil. For a displacement BEST AVAlLABLE COPt from the axis of 14 and 16, the maxima of the resultant synchronizing torque will be in excess of its negative maxnna. This condition is still further improved and the nega: tive maxima of the resultant torque still further reduced as comparedto its positive maxima by so dimensioning 14 that with the brush voltage available during the synchroni. 'ng period and an appropriate set ting of the resistance 15 this winding will develop a larger positive synchronizing torque than the windin 16. This consideration shows that in or er to get 21511111101111 a resultant torque as possible and particularly in order to reduce the maxima of the negative tor ue impulses to less 'than the maxima of t is positive torque waves, it is necessary to have the brush axes coincide as nearly with the axes of 16 and 14 as the desired operating characteristic will allow. Whenever the negative maxima of the resultant synchronizing torque do not exceed about 18 per cent of its posit vemaxima said synchronizing torque Wlll. be foundlnghly satisfactory in practice and can considered as substantially unidirectional. At that time the amplitude of the unidirectional component of the resultant synchronizing torque is abouttwice that ofits'double frequency alternating component.

In order to more clearly explain howthe operating or compounding or power factor characteristic can be atl'ected. reference will be had to Fig. 2 which shows a motor heretotore proposed. I have discovered that satisfactory compounding cannot 'be obtained unless the "ampereturns in 1 1 and 16 are given a ratio which differs from the ratio of the compounding to the exciting voltages impressed on these windings. Assuming a motor with the constants underlying, the phase and space diagram of Fig. 3, it is easy to calculate that in order to preserve unity power factor. from, say, .5 to 43' amperes, it is necessary for the unidirectional magnetization, -or the total ampereturns, produced by the secondary windings 1'4, 16 to rise in the proportion of 1 to 1.52, whereas the compounding arrangenient of Fig. 2 onlyyields a rise of 1 to 1.17 if the ratio of the unidirectional ampereturns in 14 and 16 is 1 to 10 or the same as that of the voltages which determine said am'pereturns. the ratio of ampereturns in 1 t to that in 11; 1s made 1 to 5 wheii the ratio of, the coinpounding to the exciting voltage is still 1 to 10. then the change in the sum of the xcit mg and compounding'ampereturns. which, disregarding saturation, is proportional to F, would vary from 1 to 1.48 it produced the exciting and compounding voltages; available when the actual unidirectional flux" F in the machine is generated by means of separate excitation and varied so as to keep the power factor at unity for all loads. If, under the circumstances named, the sum of said ampereturns rose from 1 to 1.52, it would indicate that the machine would automatically produce unity power factor at?) and at 43 amperes load, although the power factor might difi'er from unity for intermediate current or load values. This is merely a simple way of explaining the ef-- fect of the adjustments forming part of the present invention and the above assumption underlies all the following explanatory statements relating to the variation of the compounding and the exciting voltages andsecondary ampereturns with varying load.

The vector diagram of Fig. 3 is drawn for. a current of 30 amperes and on the assumptiont'hat'a vector leading another is to be'shown in advance of the latter in' a clockwise direction; 'For unity power factor. the current a will be in phase with the terminal voltage E The phase displacement and magnitude of the back E. M. F. E.- is determined by the electrical time constant of the primary an'dthe resultant magnetization R must be at right angles to E, and lead'same. The phase or-space position of F. the total unidirectional magnetization produced. by 14 and 16., is found as the. second side of a parallelogram of which the armature reaction AB is theother and R the resultant. 'AR can be represented by the same vector as the primary current For sor'neload and excitation the vectors R and F are alsoshown in Fig. 2 in their correct spacc'relation to "the axes of the exciting and compounding windings and to the two brush axes. It will'be seen that as the load decreases R and F come closer 'and closer together withoutever coinciding in a prac- -tic al mach ine and while F always remains coaxial with 14 and 16. Since the brush 7 pendicular to 'F'a-nd the exciting voltage is proportional" to. that component 020 of R which coincides with F.

If the compounding brushes 10, 11 are removed. as shown in'Fig; 4, andF varied from 1 to 1.52 independently of the voltage at the-brushes l2, 13'and as necessary to preserve unity power factor from 5 to 43 amperes load, the voltage at the brushes 12, 13- would vary from 1 to Q5 showing that. if

ees

1' AvinLAeECO said brushes were connected to the winding 16 the combination could not be operated at anywhere near unity or leading power factor over any range of load.

Now I have found that the compounding characteristic can also be varied by displacing the brushes as shown in Figs. 5. 6.1 0 or 9 and with the following results. Again assuming that in all cases F is in some way varied with the load current so as to preserve unity power factor the sum of the exciting and the compounding voltage will then vary from 1 to 1.32 if the'compoundiug voltages. The vector 0-25 as coinpared to 0.-21 of Fig. 3 shows the change in the corresponding voltage when the compounding brushes are moved 2Q degreesagainstrotation of the primary as in Fig. 'When moving the compounding brushes in this direction a position is soon reached for which the compounding voltage'will be negative at light and positive at heavy loads. producing through the winding 14 a dernagnetizing action in the first and aura nct-izing action in the second instance. i 1

If the compounding brushes arc-shi fted :2 degrees in the direction of rotation of the primary. as in 'Fig. 6. then vector ()23 of Fig. 3 will indicate the change in the com.- ponnding voltage and the resulting change in the sum oftheexc'iting and m orium}; voltages is from 1 to;1.07,'whrch good as in the case of Fig.2.

S milarly, 1n.F1g. 7 the exciting brushes are moved degrees against rotation. The

magnitude-of the" exciting voltage changes from.020-to ()124.in Fig. 3' and the result is ab llt the same as inlFig, 5, the sum of tue 'voltages varies from 1. a 1.31..

in Fig. 8 th excitingbrnshes are moved- 2() degree-s in ie direction of: rotation, the

exciting voltage is now represented by the vectorii22 of Fig. 3 and the sum of'th voltages varies from 1 to 1.07.

I In Fig. 9 the exciting and the compound- 'in'g' brushes are both moved 20 degrees against rotation. see vectors ()24; and 025 of Fig. 3. and the sum of thevoltages varies from 1to1.53.v I i This clearl indicates whatcan be achieved by tie displacements shown and without resorting to a modification in the ratio of exciting and compounding ampereturns as compared to the ratio of the corresponding voltages.

There 1s one more pointof interestin connection with the location of the brushes. \Vhen located as shown in Fig. 2, namely in line with and at right angles to the axis of 14, then the compounding voltage is very small at no load and will usually not reach a maximum at full load while the exciting voltage a maximum at no load and diminishes 'as the load increases. This means that at full load or maximum load the copper of the commuted winding -will be poorly utilized because ot'the great discrepancy in the compounding and exciting voltages. \Vhenevcr conditions permit.

1 therefore prefer to set the compounding brushes a little ahead of the axis of 1 1, when the primarv revolves, and the excitingbrushes a little back of the perpendicular to that axis as shown in Fig. 1. .In this way the magnitude of the compounding and ofthe exciting voltages is made more nearly equal at full load. This can usually be done without -sacrifice of the power factor characteristic and at a dis tinct gain in so far as synchronizing torque is. concerned,,particularly when the ratio-of exciting to compounding ampere;

turns is made to differ from theratio of thecorrespondingvoltages: 1

".ll'h'e-n the axis ofcither-brush set isidis placerhwithrelation to the axis of the exciting and compounding windings 16 and H, then the phase ofthe voltage appear ing at llvhis set of brushes at sub-synchronous speeds and dn'e'to the revolviimilux.

setup bythe primary member will c range -\vith relation to the phase of the voltage generated in, either secondary-winding H or16 by this same primary. revolving flux. \Yhen the brush axis is coaxial with the axis of a secondary winding, then the brush voltage at speeds near tl1e.'synchr0nous"will be cophasal with. the vo .tage' generated'iri said secondary. \Vhen the brush axis is displaced-1 b'ySJO electric'alde'grees' from the "axis of asecondary winding then the brush voltage near synqhronism will be in phase quadrature with the voltage generatedin said secondary. when the primary revolves and the brushes are connected and. displaced as shown in Fig. 1, fhcn'the voltage appearing at the brushes 10, ll'leads the voltage generated in 14 and the voltage appear ing at the' brushes 19.. 13 leads .t hat generated in the "winding 16'. \Vhen the brushes 10. 11'are' displaced as shown in Fig. 5, the voltage appearing at: saidbru'shes lags behind that generated in '14 at speeds near-thesynchronous by the revolution of the flux set up by the primary Instead of expressing the desired relation between the axes of the secondary windings and the axes of the brushes to which they are connected in terms'of space angles, this relation can be just as positively specified bv reference to the phase of the brush volt winding 2' of Fig. 1 as separate from thethree-phase winding 3 is to indicate that as a rule these two windings must be designed for ,very difierent voltages. In order to secure good commutation and avoid dangerously high voltages in the windings 14 'and 16 at starting, it is necessary to make the maximum brush voltage much smaller than even the lowest usual distribution yoltage applied to 3. There are various known modifications of; such windings and these may be used instead of the arrangement shown in Fig. 1 without modifying the mode of operation of my improved motor.

Whilethe discussion of the' various conditions governing brush displacements and other adjustments are referred to a machine with revolvin primary, and su'chare illustrated, it will be understood thatthe primary may just as, well. be stationary, 1n

wliich ease the secondary will revolve.

It is'to be understood that'a synchronous motor is-amachine capable of operating at a constant and synchronousspeed under vary ing load conditions and which does so operate. The synchronous motors described in this specification carry unidirectional ampereturns on their secondary and unless the organization of the machine is such as to-pen mit, with changing torque demand, (1).of anangular displacement between the axis of said ampereturns and the axis of theresultant motor magnetization, or (2) of a change in the nagnitude of said ampereturns or (3) of said angular displacement and of said change in magnitude, the motor cannot and does not run at a constant and synchronous speed under varying load conditions.

It is further to' he understood that by synchronous'torque is meant a torque exerted by a synchronous motor when in normal operation and therefore when running synchronously under load. By synchroniz-.

mg torque is meant any torque adapted to or capable of bringing'up to synchronism a motorcapable of operating synchronously under varying load conditions. It is, for instance, known that an ordinary polyphase induction motor is a non-synchronous machine the torque of which falls off very rapidly assynohronism' is approached and actually becomes zero'at synchronisin, It is also known- SEST AVAZLABLE CDPE modified as to make it capable of operating synchronously under varying load conditions. any torque which, in a polyphase induction motor adapted to operate synchronously imder varying load, will bridge the gap between the induction motor torque of the machine, which becomes zero at synchronism, and its synchronous torque is referred to'as a synchronizing torque. p

A synchronous motor is said to be compounded when the unidirectional ampere turns on-the secondary. are smaller at light than at heavy loads. This change in the unidirectional ampereturns with changing load affects the power factor at which the machine operates. The change can be such that the power factor remains practically constant throughout the synchronous load range of the motor, or it can be 'suchthat the power factor is a leading one at light loads, that this lead diminishes with increasing load and is converted into a lag near the maximum synchro nous torque of the machine. Either of these f compounding characteristics are po ular and right now the last named is pro ably more in demand.

While a theory has been advancedin connection with the machines referred to'herein, this has been done with a view to facilitating their descri'tion and understanding and it is to be -un erstood that I do not bind. myself-to this or any other theories- It will be clear that various changes may be made in the details of this disclosure without departing from the spirit of this invention, and it is, therefore, to be understood that this invention is not to be limited-[to the specific details here shownanddescribd. In the appended claims I aim to cover all the modifications which are within the scope of my invention.

Having thusdescribed the invention, what is claimed is: 1. The method of operating a motor which carries variable load at synchronous speed,

comprising, producing auxiliary voltages which are unidirectional at synchronism and whichvary in magnitude when the motor load yaries, impressing these auxiliary voltages on the secondary to produce coaxial magnetizations, and causing the resultant of revolves with respect to the primary, causing the primary flux to generate inductionmotor-torque producing ampereturns' in a secondary c1rcu1t,'producing-two auxiliary voltages of slip frequency which differ in phase below .synchronism and become unidi- 'rectional at synchronism, impressing one of these auxiliary voltages o'n' 'a secon ary cir-' that a polyphase induction motor can be so'fcuit'to produce a synchronizing torque and 'r'ectional magnetizations to so vary with varying load as to increase the total'secondary unidirectional magnetization with increasing load.'-

3. The method of operating a motor which carries varying load at synchronous speed, comprising, producing a primary flux which revolves with respect to the pr1mary, causing the primary flux to generate inductionmotor-torque roducing ampereturns in displaced secon ary circuits, producing two auxiliary voltages of'slip frequency which differ in base below synchronism andbecome unidirectional at ,synchronism, impress-' ing one of these auxiliary voltages on an induction-motor-torque producing secondary motor-torque circuit to roduce a synchronizing torque which reac es :1 maximum when theslip frequency auxiliary voltage is at or near amaximum and to produce'during s nchronous operation a part of the secon ary uni directional magnetization, impressingthe otherof said auxiliary voltages on anotherv circuit on thev secondary to produce during synchronous operation another art of the secondary unidirectional magnetization, and 4 -causing both of these" unidirectional -mag-. 7 netizations to so vary with varying load as e to increase the total secondary magnetization with increasing load. 4. Themethod of operating a motor which carries varying load at synchronous speed, ,comprising, roduciiig a primary flux which revolves wit res ect to the primary, caus-' ing the" primary ax to generate inductionroducing amper'eturns in dis-'- placed secon ary circuits, (producing two auxiliary voltages of slip frequency, which differ in phase-below synchr'onism and he come unidirectional at synchronism, impressing one of these auxiliary voltages- 'on one of the induction-motor-torque producing circuits,- to produce a synchronizing torque and durin synchronous operation ,a part oi the secon ary unidirectional magnetization, impressing the other of said auxiliary volt:

' ages on another circuit on the secondary to produce during'synchr'onous operation another ,part of the secondary unidirectional ma etization along anaxis substai tially co incrding with that of the first part of said; magnetization and caus ng both. of these secondary unidirectional. magnetizations to so vary with varying load as to increase the total secondary magnetization with increasing load. 4 i

5. A motor which carrles variable load at synchronous speed,

having a. primary and ,member coaxial windings in induc'-- m T AVAlLABLE (30px,

secondary, means for roducing auxiliary voltages which are unidirectional at synchronism and which vary in magnitude when the motor load varies, coaxial windmgs on tllQSECODd'dI), and means for impressing said auxiliary voltages on said coing, adapted to make available auxiliary voltages which are of slip frequency near synchronism and unidirectional at synchronism, and displaced brush sets bearing on saidcOmmutat r and connected with-said coaxial windings and adapted to impress on said windings auxiliary voltages of such phase as to produce near synchronism a synchronizing torque and at synchronism a r sultant .unirectional magnetization which in-, creases with increasing synchronous load.

7; A motor which carries-variableload at synchonous speed, comprising, a primary memberv having a winding, a secondary member having coaxial windings in induc tiverelation to said primaryl winding, 9. commutator cooperating wit said primary winding, adaptedto make available auxiliary voltages which are of slip frequency near synchronism and unidirectional at synchronism, and*displaced"brush sets bearin on said commutator and;connected with sai coaxial windings, said brush setsbeing ositioned to impress; on said coaxial'win gs voltages of ubstantiall less than quadrature phase relation to the voltages induced in said coaxi l windings near synchronism.

8; A motor which carries variable load at synchronous speed, comprising, a primary member having a winding, a secondary memher having coaxial "windings in "inductive relation to said primary winding, a commutat'or cooperating with said primary-wind- 1 ing, adapted "to make available auxiliary voltages which are of slip frequency near synchronism and unidirectionalat synchronism, and -di'splacedb hsets bearing on said commutator and connected with said coaxial-windings ,,said brush sets being positioned to iinpress on said coaxial windings voltagesof substantially less thanquadrature phase relation to and leading the voltagesinduced in said coaxial win ings near synchronism. Y L -f I 9; A motor-which carries variable load at synchronous speed, comprising; a primary member having a winding, 9. se'condar' connected to one of said secondary windings' and displaced from the axis thereof.

10. A motor whichcarries variable load at synchronous speed, comprising, a primary member havinga winding, a secondary member having coaxial windings in inductive relation to said primary winding, a commutator cooperating with said prima winding, adapted to make available auxi iary voltages which are of slip fr uency near syn chronism and unidirectiona at synchronism, sets of brushes bearing on said commutator, each set being connected to one of said sec ondar windings and displaced from the axis t ereof, and said sets being displaced from each other by an angle other than ninety e-lectricaldegrees.

11. A- motor which carries variable load at synchronous speed, comprising, a primary member having a winding, a secondary member having coaxial windings in inductive relation to said primary-winding, said rimary member bein auxiliary voltages w ich are unidirectional atsynchronism, and means for'impressing the auxiliary voltages on" said secondary windings, the ratio of ampereturns roduced in said secondary windingsdifiering from. the ratio of the voltages impressed thereon;

12. A motor which carries variable load at synchronous speed, comprising, a primary and I a secondary member. without defined polar projections, the primary member having a-winding adapted to produce a prima flux which revolves with respect to-thepru polar projections, the primary member hava winding adapted to produce a primary flux which revolves withrespect to the primary, means includingtwo displaced brush sets for causingthe primary flux to-prodiicetwo auxiliary voltages, substantially coaxial exciting and compounding windings on the secondary .member, said brush sets being so connected I and positioned and the exciting andlcompounding windings so dimensioned that the positive maxima of the resultant synchron zadapted to pro uoe ing torque produced by said windings exceed the negative maxima thereof.

14. A motor which carries variable load at synchronous speed, comprising, a primary and a secondary member without defined polar projections, the primary member having a windin adapted to produce aprimary flux whic revo ves with respect to the primary, means including two displaced brush sets for causing the primary flux to" roduce two auxilia voltages, substantially coaxial exciting an compounding windin on the secondary member, one set of brus es being connecte to the exciting and the other to the compounding winding, said windings be ing so dimensioned that for equal brush yolt ages the ampereturns in the com unding would be greater than in the exciting winding. 15; A motor which carries variable load at synchronous speed, comprising, a rimary and a secondary member without de ed p0- lar projections, the primary member having a winding adapted to produce a prima flux which-revolves with respect to theqprimary, means inclnding -two-displaced bl-ush sets for causing the primary flux to gener-' ate two auxiliary voltages which become unidirectional at synchronism, substantiall coaxial exciting and compounding win ings on the secondary member, one set of brushes being cgnnected to the exciting and theother to the'compoundin winding and the ratio of the unidirectiona ampereturns in the two windings difiering in synchronous operation from'the ratio of the brush voltages producing said ampereturns. a

16. In a motor which carries variable ldad at synchronous speed, a primary and asecondary without defined polar projections, 21

commuted'and another winding on the pri;

mary, said other winding being adapted for connection to an alternaging'current supply,'1-

two displaced sets of br shes carried by the secondary and co-operating with the com-" muted winding on the primary, a compounding and a substantially coaxial' exciting :winding on the secondary, each of said c,o- V

axial windings beingconnected to'one set of brushes, that set w ch ,is conn ected to the exciting winding: being displaced from the perpendicular to the axis of said winding.

17: In a motor whichcarries variable load at synchronous s eed, a primary and a sec-- ondary without efined polar projections, a commuted and another winding on the primary,-s'aid other winding being adapted for substantially coaxial exciting winding on the secondary, each of said coaxial windings being connected to one set of brushes, said brush sets being displaced by an angleother than ninety electrical degrees one from the other.

18. In a motor which carries variable load at synchronous s eed, a primary and a secondary without efined polar projections, a. commuted and another winding on the primary, said other. winding being adapted for.

Connection to an alternating current supply, two displaced sets of brushes carried by the seconda and cooperating with the'commuted winding on the primary, a compounding and a substantially coaxial exciting axial windings being) one of the brush sets, another windin windin on the secondary, each of said cobrushes, both sets eingdisplaced by less than ninety electrical degrees from the axis of the coaxial-secondary windings.

19. In a motor which carries variable load I speed, a'primary and-a secsecondary coaxial with that connecte to one brush set and itself connected to the other said secondary windingsbeing connected to brush set, a' resistance shunting one of the coaxial windin and another .shuntin a secondary win ing located along anoter axis. i 20. In at synchronous without a motor which'carries variable load eed, a primary anda secefined polar projections, a

ya connection to an alternating current supply,

two sets of brushes carried by the seconda and co-o crating with the commuted win ing on t e primary, a polyphas'e arrangement of windings on the secondary,-one of one of the brush sets, another windingv on the secondary coaxial with to one brush set and itself connected to the other brush set, the two brush sets being displaced by less than ninety electrical degrees one from the other and a resistance shunting a winding on the secondary displaced from the coaxial windings thereon.-

2-1. In a motor which carries variable load at synchronous s eed, a primaryand a secondary without efined polar projections, a commuted and another winding on the pri- .rnary, said other winding being adapted for connection to an alternating current supply, two sets of brushes carried the secondary and co-operating with the-commuted winding on the primary, a compounding and a substantially coaxial exciting windingon the secondary, each coaxial winding being connected to one set of and a secondary member without defined polar projections, the primary member being on the that connected connected to one set of brushes, the brushes connected to the compounding winding being positioned to collect a voltage of one direction at one load and a voltage of the opposite direction at another load. a

22. In a motor which carries variable load at synchronous speed, a primary and a secondary without defined polar projections, a commuted and another winding on the primary, said other winding being adapted for connection to an alternating current supply, two displaced sets of brushes carried by the secondary and co-operating with the commuted winding on the primary, a compounding and a substantially coaxial exciting A winding on the secondary, each coaxial winding being connected to one set of brushes, the brushes connected to the exciting winding being positioned to collect substantially less than the maximum available unidirectional voltage at no load.

23. A-,motor which carries variable load at synchronous speed, comprising, a primary adapted for connection to an alternating current supply, means including two dis laced brush .sets for causing the primary ux to produce two auxiliary voltages, substantially coaxial exciting and compounding windings on the secondary member, one'set of brushes being connected to the exciting and the other to the compounding winding, said winding}? being so dimensioned thatioiequal bru the ampereturns in the compound- W voltages ing would be greater than in the exciting winding. I I 24. A motor whichcarries variable load at synchronous speed, comprising, a primary and a secondary member without defined polar projections, theprimary member being adapted for connection to an alternating current sup ly, means including two displaced brus flux to generate auxiliary voltag come unidirectional atisynchromsm, substantiall coaxial excitin and compounding, win ngs on the secondary member, one set of brushes being connected to the exciting and the other to the com ounding winding, and the ratio of'the uni irectional ampereturns in the twowindings differing in synchronous operation from the ratio of the brush voltages producing said ampereturns.

' 25. A synchronous motor comprising, a primary memberhaving a winding a secondary member having coaxial windings in inductive relation to said primary winding, said primary member being adapted to produce auxiliary voltages which are unidirectional at synchronism, and means for impressing the auxiliary voltages on said secondary windings, the maximum number of ampereturns produced by one auxiliary "voltage 111 one of the secondary windings sets for'causing the primary es which be- I differing from the maximum number of ampereturns produced by another auxiliary voltage in another secondary winding.

A synchronous motor comprising, a primary member having a winding, a secondary member having coaxial windin s in inductive relation to said primary win ing, said primary member being adapted to produce auxiliary voltages which are alternating at subsynchronous speeds and unidirectional at synchronism, and means for im-, pressing the auxiliary voltages on said secondary windings, the num er of ampereturns produced by the auxiliary voltage the phase of which at subsynchronous speeds more nearly approaches the phase of the voltage generated in the coaxial secondary windings being in excess of vthe ampereturns produced by the other auxiliary volt age.

27. A synchronous motor comprising, a

primary member having a windmg, a Sec ondary memberhaving two coaxial Vindings in inductive relation to said primary winding, said primary member being adapted to produce auxiliary voltages which are unidirectional at synchronism, two sets of brushes located along displaced axes to collect the auxiliary voltages each set being connected to one of the windings the set whoseaxis is nearest to the axis of the secondary windings being responsible for more ampereturns than the other set.

28. A motor which carries variable load at synchronous speed, having a primary and.

the secondary in ina secondary, circuiton coaxial secondary 't-ional magnetization east AVAlLABLE cos:

ductive relation to the primary, a source adapted to make available auxiliary voltages which near synchronism are of slip frequency and differ in phase and which be come unidirectional at synchronism, "and means for impressing difierent auxiliary voltages on different-secondary circuitsto produce unidirectional ampereturns in said circuits at synchronism, so dimensioned that for auxiliary voltages of equal magnitude the ampereturns in one secondary circuit exceed the ampereturns in another secondary circuit.

29. The method of operating a motor which carries variable load at synchronous speed, comprising, producing a primary flux which revolves with respect to the primary, causing the primary to generate induction-motor-torque producing ampereturns in a secondary circuit, producing two auxiliary voltages of slip frequency, of an am litude independent of their frequency, wh ch difier in base below synchronism and become uni lrectional at synchronism, impressing one of these auxiliary voltages on the secondary circuit to produce a synchronizingtorqueand a unidirectional magn'etization at synchronism, and impressing the other auxiliary voltage onanother secondary circuit to produce another unidirecat synchronism which is substantially coaxial with the first unidirectional magnetization. In testimony whereof I this 16th day of February, 1924.

VALEBE A FRE FYNN;

said circuits being ailix my signature 

